muskrat
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Muskrat ( Ondatra zibethicus ) |
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The muskrat ( Ondatra zibethicus ) or the muskrat is originally exclusively in North America -based rodent species , which, starting from Bohemia and later France over most of Europe and Asia spread and as a new type ( neozoon has established). The term muskrat is misleading, because zoologically, the muskrat is not a type of rat . The muskrat is one of the voles (Arvicolinae), of which it is the largest living representative.
Musk is another name for musk , one from the Siberian musk deer ( musk moschiferus fragrance generated). The muskrat owes its name to a musky-scented secretion that the preputial glands of the males secrete.
The as muskrat called fur muskrat is an important article of commerce of the fur trade , depending on the mode in varying degrees.
The popular names of the muskrat also include the names musk rat, dwarf beaver, muskrat, civet rat, swamp rabbit, swamp hare and water rabbit. The muskrat is sometimes confused with the nutria .
Morphology and characteristics
With a head-to-trunk length of around 35 cm and a tail length of around 22 cm, the muskrat is smaller than a nutria ( Myocastor coypus ) or a beaver ( Castor fiber ) and larger than a brown rat ( Rattus norvegicus ). The weight is usually between 0.8 and 1.6 kilograms (maximum: 2.3 kilograms). The muskrat is stocky, rat-like shape. The short and thick head goes outwardly into the trunk without a neck. The tail is almost bare and flattened on the sides.
The muskrat is well adapted to aquatic life. It has waterproof, closable ears , the ears of which are hidden deep in the fur . Although their rear paws , unlike beavers and otters no webbed exhibit is the muskrat a skilled swimmers and divers. Instead of webbed muskrats, muskrats have so-called swimming bristles: stiff hair that grows as a hem on the edges of the toes and thus enlarges the toes like a paddle. The main drive when moving in the water is provided by the long, powerful legs and the widely spread rear feet. The muskrat uses its tail, which it moves to the right and left in a horizontal plane, to control and support its swimming movement. Their fur is very dense and water-repellent, so that they can often stay in the water for long periods of time.
Muskrat meat is edible. Their fur is very valuable to the fur industry. It varies from black to dark brown to cream-colored, there are also some albinos , so it applies in some countries such as B. the USA as a valuable livestock, hunting and breeding animal. Their habitat is on the water.
behavior
Way of life
Muskrats are mostly in the water. They are excellent swimmers and can dive for up to ten minutes. On land, however, the muskrat looks rather clumsy. The shy animal adopts almost any reasonably suitable flowing and still water as a habitat. Muskrats are usually active at night and at dusk. As with many other animal species, such as the red fox and wild boar , the day and night rhythm is dependent on disturbances by humans. In areas where they are relatively undisturbed, they can often also be observed during the day.
Optical and olfactory signals play a role within the species . The male deposits feces at the territorial boundaries during the breeding season. During this time, the paired preputial glands , in which the musk secretion is produced, also enlarge significantly . The muskrat seldom utters sounds. During mating, both animals sometimes make squeaking noises and the nestlings beep similar to mice. When confronted with conspecifics or when threatened, muskrats beat their incisors in rapid succession and thus produce a widely audible noise.
Muskrat
Muskrats have two different forms of burrow. The type depends on the habitat.
Wherever there is a bank section, muskrats dig earthworks as shelter, the entrances of which are under water. If the water level rises or falls, the entrance is placed higher or lower accordingly. In doing so, they often undermine dykes , dams and fortifications , which can cause major problems for hydraulic structures. They use their front paws as well as their incisor teeth to dig. From the entrance to the building a tube leads diagonally upwards and ends in a boiler.
Where the biotope does not offer the possibility of building such an earthworks, muskrats build dwellings 0.5 to 2 meters high from reeds and other aquatic plants such as rushes and reeds , the so-called "muskrats". The nest hidden in it is only just above the water level. The shape of the castles is mostly frustoconical, the base is circular to elliptical; the pipe that leads to the boiler is under water, as in the earthworks. Larger castles are occasionally inhabited for several years.
food
Muskrats feed mainly on aquatic and bank plants. Commonly eaten plants include reeds , cattails - rushes - lake and pond rose species and tree bark, horsetail - and pondweed species . However, they also go for grains , vegetables , fruits and grasses and dig for the tubers of Jerusalem artichoke . In the months with little vegetation, they supplement their diet with mussels , larvae of aquatic insects, crabs , water snails and, more rarely, frogs and fish . However, the preferred food is plant-based even at this time. During this time they prefer to dig for plant roots.
The claim that muskrats also eat birds or their eggs could not be confirmed. The share that mussels and crabs have in their prey is also controversial.
Life expectancy and predators
In the wild, only a few muskrats reach the age of three. In animals between the ages of 30 and 36 months, the crowns of the molars (molars) are usually chewed down to the root neck, so that the animals die due to poor nutrition. In contrast, 85 percent of a population at the beginning of the reproductive period consists of animals that were born in the previous year. High rates of loss occur especially during the migration of the animals. During this time, they are exposed to greater enemy pressure than when they are in an established area. The mortality of the animals is also very high during the time of the establishment of the territory before a breeding period.
Otters ( Lutra lutra ), eagle owls and the red fox hunt rodents. In Sweden it has been found that in years after a vole gradation , muskrat populations also decline. This is due to the fact that after the collapse of a very large vole population, the enemy pressure on the muskrat populations is very high.
Predator-prey relationship between mink and muskrat
The most important predator of the muskrat is the American mink, the mink ( Neovison vison ), also imported from North America . Extensive studies of the complex predator-prey relationship between muskrat and mink are available by the zoologist Paul Errington , who has dealt with the ecology of the muskrat in the wetlands of Iowa for more than 30 years . Minke and muskrats are similar in body size, have a similar semi-aquatic way of life and the same habitat preferences. Minke have a slightly larger body length, but full-grown muskrats are built a bit more massive. Minke prey on muskrats by grabbing them with their front legs and biting them repeatedly in the head and neck. Although muskrat is the preferred diet of minke, Errington has shown that minke decimation is not a factor limiting muskrat populations. Muskrats' territorial instinct determines how many individuals can find sufficient food and space to build burrows in a habitat. As soon as the habitat is full and a very high population density is reached, the mortality of all other muskrats increases. The mortality rate is particularly high among muskrats who immigrate from the surrounding area or are weakened by disease and age or who have to look for territory as young animals. Mainly these animals are captured by Minken. In the investigated area in Iowa, 70 percent of the muskrats hunted by minks were weakened by disease or extreme climatic conditions. A significant percentage of the prey were male muskrats, who abandoned their burrows in spring and migrated to unfamiliar areas in search of new territories for the summer breeding season. Just as often, young animals for which there was not enough food in their habitat fell victim to the minks, while healthy, adult muskrats, which occupy nutrient-rich territories, rarely fell victim to it. The population dynamics of muskrats is therefore described as density-dependent - there is a fundamental difference for the mink between the total number of muskrats in an area and the individuals available as potential prey. Muskrats living in advantageous ecological positions remain largely undisturbed.
Reproduction
During the breeding season, muskrats occupy a territory that they defend against their conspecifics. The size of the area depends on the respective feeding conditions. An area is on average between 3,000 and 5,000 square meters.
The muskrat can reproduce all year round in climatically favorable habitats. This can be seen, for example, in the southern regions of the USA. The breeding season in Central Europe is usually from March to September. However, pregnant females and young animals have already been observed in Central Europe during the winter months. As a rule, there are two litters in Central Europe during a year. If the environmental conditions are very good, a third throw is also possible. The wearing time is 30 days. Litters consist of four to nine boys. The normal litter consists of five to six young animals. In the following year, the young are sexually mature again. Your - very fast - spreading occurs along their natural habitat, ie upstream and downstream along streams and rivers.
Boys weighing around twenty grams at birth are born blind and naked. The young animals develop their thick and silky nestling fur within the first 14 to 18 days; their eyes open between the 10th and 14th day of life. After about four weeks the top hairs begin to grow; this change of hair into the so-called old age dress is completed after four months. The animals have then reached a weight of about 600 grams. The young animals are raised in the residential castles.
distribution
Original distribution area
The original range of the muskrat are the wetlands of North America. In the United States, the muskrat even lives in the tidal salt marshes on the Atlantic coast. The muskrat finds ideal living conditions in the larger ponds or lakes with strong aquatic plant production.
The muskrat was able to compensate for the decline in natural habitats in North America by now living along artificially created canals. Apart from a few areas, both the US and Canada are fully populated by this species.
Spread outside North America
According to generally accepted opinion, the first colonization of Europe and Asia came from Bohemia in what is now the Czech Republic . Prince Joseph Colloredo-Mansfeld brought three females and two males of the muskrat from Alaska from a hunting trip in 1905 . According to morphological studies, however, the animals released are the nominate form Ondatra zibethicus zibethicus, which is represented in eastern Canada . He released the animals in the Huťský rybník (German hut pond) near the Bohemian Stará Huť (old huts) on his Dobříš estate , around 35 kilometers southwest of Prague . From there they spread at great speed in all directions: in 1912 they had settled almost all of Bohemia, in 1915 the first appeared on the Regen in Bavaria , in 1927 they had broadly reached neighboring countries and spread over an area of around 200,000 square kilometers. In 1935 they were sighted in Stendal and in 1936 in Magdeburg . It spread along streams and rivers such as the Elbe and the Weser . The whole of the Czech Republic, Slovakia , Hungary , Poland , Romania , the northern part of Yugoslavia and other countries were settled from the “Colloredo-Mansfeld” population.
The largest overseas transport of muskrats was made in 1929 by a Leipzig company from Canada for the Soviet Union. In Leningrad, around 900 animals were taken over by Professor Pëtr Alexandrowitsch Zoege von Manteuffel, director of the Moscow Zoo. A small part came to the Pushkino experimental farm . The largest part was released in groups of 20 to 50 animals in suitable river areas of the taiga zone of European and Asian Russia - as far as the Far East.
Another invasion , important for the settlement of the Eurasian habitat , started in 1930 from a breeding facility in the Leval pond near Belfort in France. About 500 muskrats escaped there. These captive refugees reached northeastern France very quickly using the Rhine-Rhône Canal and the Ill . Large parts of the west of Germany were then settled via the Palatinate and Baden .
These and other releases in Belgium , Sweden , Finland , Poland and Russia accelerated the spread of the muskrat. Many of the releases were deliberate. For example, muskrats from Germany, Czechoslovakia, the USA and Canada were imported several times into Finland from 1919 and released in around 300 different locations with official approval. Again, 1636 animals had been exported from Finland to Russia by 1932. From Siberia , the muskrat reached Mongolia , the Republic of China and Manchuria . After Japan , the muskrat was introduced in 1945. This extremely successful species conquered large parts of the Eurasian continent in just a few decades and is now more widely distributed there than in its ancestral home North America.
In addition to Eurasia, muskrats have also been introduced to Argentina and Chile and have become indigenous there as well.
The success of the muskrat's spread was favored by its origin from a similar climatic area, its high reproduction rate and the pronounced wanderlust. In the new habitat there is also a lack of predators who specialize in them.
The muskrat as a neobiont
Despite their temporarily economically valuable fur with the long, shiny outer hair , the muskrat is usually classified as a pest to be controlled in Germany , especially in river and coastal regions . If the Central European muskrat catcher makes the effort to fur the captured animals, he can still sell the fur to the fur trade at a mostly low price; There is currently no longer any major economic interest in animal fur. The invasion biologist Ingo Kowarik is of the opinion that the muskrat, as a neobiont, occupies a niche in heavily used landscapes , and comes to a differentiated picture of the harmful effects. Sections of the population who do not have to bear the burden of dike protection partly follow the assessment in other countries that tolerate or even protect the muskrat. The muskrat was added to the list of invasive alien species of Union concern for the European Union in 2017 .
Arguments about the muskrat in European ecosystems
Invasion biologists believe that ecosystems are unsaturated in terms of biodiversity. Neophytes and neozoa can either occupy niches in these ecosystems that have never been occupied by native animal and plant species, or those of species that have meanwhile been pushed back by anthropogenic causes. According to Ingo Kowarik (see lit.), the great success of the muskrat's expansion can be attributed to such an unoccupied or no longer occupied niche. Another medium-sized, semi-aquatic herbivore no longer occurs in Germany. Against this background, a picture of the impact of the muskrat on central European ecosystems emerges, differentiated according to interests.
The burrowing activity of muskrats in the inland restores the original diversity and dynamism of the banks. Damage caused by muskrats on natural banks is insignificant, especially since they do not settle in floodplain areas.
Muskrats can cause considerable changes in small biotopes, changes that are relevant to nature conservation due to muskrats have not yet been found to be beneficial according to Kowarik's studies. According to this view, the reduction in reed stocks, which often occurs when muskrats occupy a habitat, tends to lead to an increase in biodiversity . The reduction in the reed stock has the consequence that reed-breeding bird species such as pond warbler and bittern are deprived of their breeding space and migrate. The resulting open water areas are quickly colonized by floating leaf plants and other water bird species. From Kowarik's point of view, the effects of muskrats as a predator of large mussel species have not been adequately investigated. For an objective judgment there are no comparisons between undisturbed mussel populations and populations used by muskrats. Here, too, the otter , which used to use these species as a source of food, has now largely been displaced and the muskrat has re-occupied this niche.
Another ecological problem is that the rodent is an intermediate host of the fox tapeworm ( Echinococcus multilocularis ): If an infected muskrat is captured by a fox , it is also infected with the parasite .
From an ecological point of view, the feeding damage caused by the muskrat is also considered. Occasionally it attacks fields and gardens or destroys wicker crops . By eating reed plants , the rodent can significantly change the structure of the flora of an entire bank ecosystem. The corresponding ordinance has since been repealed, with the first law amending the Plant Protection Act of May 14, 1998, the control of muskrats is no longer subject to plant protection law.
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Especially when the vegetable food supply is insufficient in winter, the muskrat also eats mussels and crustaceans, the population of which in Germany is already severely threatened by water pollution and river straightening. It is considered to be the main predator of the large freshwater mussels (superfamily Unionacea). B. the now very rare pearl mussel ( Margaritifera margaritifera ) counts. The collapse of stocks of the common river mussel ( Unio crassus ) in individual areas of Baden-Württemberg is also attributed to the muskrat.
Arguments about the economy of the muskrat
The muskrat settles above the waterline. It is feared because of the massive economic damage that its undermining digging activity causes on banks , dams and dykes . As a result, civil engineering and hydraulic engineering in coastal protection incur high additional costs for repair and maintenance of the dykes. For Lower Saxony , these additional costs are estimated by the State Office for Hydraulic Engineering and Coastal Protection at 1.6 million euros per year (2006). Due to the established economic damage caused by muskrats in some countries, the “Organization Européenne pour la Lutte contre le Rat Musqué”, based in Paris , was specifically set up.
Control measures
Just a few years after the muskrat was released in Bohemia, it was classified as a pest. Bavaria introduced control measures after the muskrats were first sighted. The legal basis created for this in 1917 was adopted by other German states. In 1935 a "Reich Commissioner for Muskrat Control" was appointed, which together with 36 employees remained relatively unsuccessful. Despite massive control, the muskrat is resisting extinction almost everywhere on the European continent as well as in the Asian distribution area . For a long time, both hunting and the use of bacterial pathogens could not decimate the muskrat sustainably. The muskrat is fought mainly in the Benelux countries, Germany and France .
Only in Great Britain was it possible, due to its island location , to apparently completely eradicate the bisamp population, which originally came from farms, in a short time. In 1927 muskrats were introduced there to obtain fur. In the same year some animals were able to escape. Far-reaching control measures were initiated as early as 1932, including a complete ban on imports and a ban on keeping animals. This intensive control was successful after around six years. In 1939 there were no more muskrats in Great Britain.
The first muskrats appeared in the Netherlands in 1941. The aim here is to combat the flood protection at the specified level of protection . Therefore, the muskrats were fought particularly intensively after the provinces were legally obliged to do so in 1985. Nevertheless, the population growth could not be stopped at first. This only succeeded when the length of the water body to be looked after by a full-time combatant was reduced to a maximum of 650 kilometers (corresponding to a total of 439 combatants plus management staff). The catches per field hour by the fighter are a measure of the population. In 2003 it reached its maximum with 0.85, in 2004 the largest absolute number of just over 400,000 animals was caught. In 2009 the catches per field hour had already fallen to 0.3. The absolute number of animals caught fell (with a slightly reduced number of personnel again) to 155,000. Wire trap traps are used, recently to avoid drowning, also increasingly in a floating version with bait, as well as cage-secured traps. During floods, muskrats seeking shelter on higher ground or in trees are hunted with firearms. Special traps are mostly used to catch the animals, which prevent other animals from being caught.
In Germany the muskrat must be fought all year round. The control measures are largely limited to flood protection systems, which must be protected from the burrowing activity of muskrats. The number of animals for whose catch premiums were paid with funding from the state of Schleswig-Holstein was 22,602 in 1996, 26,638 in 1997 and 41,029 in 1998.
Subspecies
Fourteen to sixteen subspecies are distinguished in North America, depending on the author. The subspecies include
- Ondatra zibethicus zibethicus , which is native to eastern Canada
- Ondatra zibethicus macrodon , the "blue muskrat" with a blue-blackish fur, which is native to certain areas of Virginia . The coat color is inherited recessively; when mixed with other subspecies, the brown phenotype therefore dominates
No subspecies are described for Europe. Animals of different subspecies were released that have mixed so that differentiation is no longer possible.
literature
- Carsten Bothe : Muskrat. Everything about muskrat: catching, fighting, trapping, recycling. Neumann-Neudamm, Melsungen 1996, ISBN 3-7888-0685-0 .
- Max Hoffmann : The muskrat (= The new Brehm library. H. 78, ISSN 0138-1423 ). Geest & Portig, Leipzig 1952 (2nd, unchanged edition, reprint of the 1st edition. Westarp-Wissenschaftliche-Verlags-Gesellschaft, Hohenwarsleben 2003, ISBN 3-89432-159-8 ).
- Ingo Kowarik : Biological Invasions. Neophytes and Neozoa in Central Europe. 76 tables. With a contribution by Peter Boye. Ulmer, Stuttgart 2003, ISBN 3-8001-3924-3 .
- Mario Ludwig , Harald Gebhard, Herbert W. Ludwig, Susanne Schmidt-Fischer: New animals and plants in the natural environment. Recognize and identify immigrant species. BLV, Munich et al. 2000, ISBN 3-405-15776-5 .
- Jochen Niethammer, Franz Krapp (Hrsg.): Handbook of mammals in Europe. Volume 2, Part 2: Heikki Henttonen: Rodentia. II (Cricetidae, Arvicolidae, Zapodidae, Spalacidae, Hystricidae, Capromyidae). Aula-Verlag, Wiebelsheim 1982, ISBN 3-400-00459-6 .
swell
- ↑ a b Paul Schöps: The beginnings of fur farming in Europe . In: Die Pelzwirtschaft issue 1, January 1979, p. 39.
- ↑ List of invasive alien species of Union-wide importance (Union list)
- ↑ Muskrat Ordinance
- ↑ Annual reports of the Landelijke coördinatiecommissie Muskusrattenbestrijding ( Memento of the original from April 5, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Landelijke coördinatiecommissie Muskusrattenbestrijding: De Nederlandse Muskusrattenbestrijding ( Memento of the original of November 4, 2010 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Combating the muskrat. (PDF; 115 kB ) Small inquiry from Dr. Christel Happach-Kazan (FDP) and answer from Minister for Environment, Nature and Forests; Printed matter 14/2614. In: landtag.nrw.de. State Parliament Information System Schleswig-Holstein, December 14, 1999, p. 2 , accessed on July 31, 2014 .
Web links
- spurenjagd.de : Muskrat - trace data collection
- Ondatra zibethicus in the endangered Red List species the IUCN 2006. Posted by: Baillie, 1996. Retrieved on 9 May, 2006.
